@article{HECHER-2017-HDY, title = "How Do Users Map Points Between Dissimilar Shapes?", author = "Michael Hecher and Paul Guerrero and Peter Wonka and Michael Wimmer", year = "2018", abstract = "Finding similar points in globally or locally similar shapes has been studied extensively through the use of various point descriptors or shape-matching methods. However, little work exists on finding similar points in dissimilar shapes. In this paper, we present the results of a study where users were given two dissimilar two-dimensional shapes and asked to map a given point in the first shape to the point in the second shape they consider most similar. We find that user mappings in this study correlate strongly with simple geometric relationships between points and shapes. To predict the probability distribution of user mappings between any pair of simple two-dimensional shapes, two distinct statistical models are defined using these relationships. We perform a thorough validation of the accuracy of these predictions and compare our models qualitatively and quantitatively to well-known shape-matching methods. Using our predictive models, we propose an approach to map objects or procedural content between different shapes in different design scenarios.", month = aug, doi = "10.1109/TVCG.2017.2730877", issn = "1077-2626", journal = "IEEE Transactions on Visualization and Computer Graphics", number = "8", volume = "24", pages = "2327--2338", keywords = "shape matching, transformations, shape similarity", URL = "https://www.cg.tuwien.ac.at/research/publications/2018/HECHER-2017-HDY/", } @article{guerrero-2015-lsp, title = "Learning Shape Placements by Example", author = "Paul Guerrero and Stefan Jeschke and Michael Wimmer and Peter Wonka", year = "2015", abstract = "We present a method to learn and propagate shape placements in 2D polygonal scenes from a few examples provided by a user. The placement of a shape is modeled as an oriented bounding box. Simple geometric relationships between this bounding box and nearby scene polygons define a feature set for the placement. The feature sets of all example placements are then used to learn a probabilistic model over all possible placements and scenes. With this model we can generate a new set of placements with similar geometric relationships in any given scene. We introduce extensions that enable propagation and generation of shapes in 3D scenes, as well as the application of a learned modeling session to large scenes without additional user interaction. These concepts allow us to generate complex scenes with thousands of objects with relatively little user interaction.", month = aug, journal = "ACM Transactions on Graphics", volume = "34", number = "4", issn = "0730-0301", doi = "10.1145/2766933", pages = "108:1--108:13", keywords = "modeling by example, complex model generation", URL = "https://www.cg.tuwien.ac.at/research/publications/2015/guerrero-2015-lsp/", } @article{Guerrero-2014-TPS, title = "Partial Shape Matching using Transformation Parameter Similarity", author = "Paul Guerrero and Thomas Auzinger and Michael Wimmer and Stefan Jeschke", year = "2014", abstract = "In this paper, we present a method for non-rigid, partial shape matching in vector graphics. Given a user-specified query region in a 2D shape, similar regions are found, even if they are non-linearly distorted. Furthermore, a non-linear mapping is established between the query regions and these matches, which allows the automatic transfer of editing operations such as texturing. This is achieved by a two-step approach. First, point-wise correspondences between the query region and the whole shape are established. The transformation parameters of these correspondences are registered in an appropriate transformation space. For transformations between similar regions, these parameters form surfaces in transformation space, which are extracted in the second step of our method. The extracted regions may be related to the query region by a non-rigid transform, enabling non-rigid shape matching.", month = nov, issn = "1467-8659", journal = "Computer Graphics Forum", number = "8", volume = "33", pages = "1--14", keywords = "Shape Matching, Texture Transfer, Non-Rigid, Deformable, Edit Propagation, Partial", URL = "https://www.cg.tuwien.ac.at/research/publications/2014/Guerrero-2014-TPS/", } @phdthesis{Guerrero_Paul_2014_EPG, title = "Edit Propagation using Geometric Analogies", author = "Paul Guerrero", year = "2014", abstract = "Modeling complex geometrical shapes, like city scenes or terrains with dense vegetation, is a time-consuming task that cannot be automated trivially. The problem of creating and editing many similar, but not identical models requires specialized methods that understand what makes these objects similar in order to either create new variations of these models from scratch or to propagate edit operations from one object to all similar objects. In this thesis, we present new methods to significantly reduce the effort required to model complex scenes. For 2D scenes containing deformable objects, such as fish or snakes, we present a method to find partial matches between deformed shapes that can be used to transfer localized properties such as texture between matching shapes. Shapes are considered similar if they are related by pointwise correspondences and if neighboring points have correspondences with similar transformation parameters. Unlike previous work, this approach allows us to successfully establish matches between strongly deformed objects, even in the presence of occlusions and sparse or unevenly distributed sets of matching features. For scenes consisting of 2D shape arrangements, such as floor plans, we propose methods to find similar locations in the arrangements, even though the arrangements themselves are dissimilar. Edit operations, such as object placements, can be propagated between similar locations. Our approach is based on simple geometric relationships between the location and the shape arrangement, such as the distance of the location to a shape boundary or the direction to the closest shape corner. Two locations are similar of they have many similar relations to their surrounding shape arrangement. To the best of our knowledge, there is no method that explicitly attempts to find similar locations in dissimilar shape arrangements. We demonstrate populating large scenes such as floor plans with hundreds of objects like pieces of furniture, using relatively few edit operations. Additionally, we show that providing several examples of an edit operation helps narrowing down the supposed modeling intention of the user and improves the quality of the edit propagation. A probabilistic model is learned from the examples and used to suggest similar edit operations. Also, extensions are shown that allow application of this method in 3D scenes. Compared to previous approaches that use entire scenes as examples, our method provides more user control and has no need for large databases of example scenes or domain-specific knowledge. We demonstrate generating 3D interior decoration and complex city scenes, including buildings with detailed facades, using only few edit operations.", month = nov, address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", school = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", URL = "https://www.cg.tuwien.ac.at/research/publications/2014/Guerrero_Paul_2014_EPG/", } @article{Guerrero-2014-GRF, title = "Edit Propagation using Geometric Relationship Functions", author = "Paul Guerrero and Stefan Jeschke and Michael Wimmer and Peter Wonka", year = "2014", abstract = "We propose a method for propagating edit operations in 2D vector graphics, based on geometric relationship functions. These functions quantify the geometric relationship of a point to a polygon, such as the distance to the boundary or the direction to the closest corner vertex. The level sets of the relationship functions describe points with the same relationship to a polygon. For a given query point we ?rst determine a set of relationships to local features, construct all level sets for these relationships and accumulate them. The maxima of the resulting distribution are points with similar geometric relationships. We show extensions to handle mirror symmetries, and discuss the use of relationship functions as local coordinate systems. Our method can be applied for example to interactive ?oor-plan editing, and is especially useful for large layouts, where individual edits would be cumbersome. We demonstrate populating 2D layouts with tens to hundreds of objects by propagating relatively few edit operations.", month = mar, journal = "ACM Transactions on Graphics", volume = "33", number = "2", issn = "0730-0301", doi = "10.1145/2591010", pages = "15:1--15:15", keywords = "Shape Modeling, Floor Plans, Edit Propagation, Geometric Relationship Functions", URL = "https://www.cg.tuwien.ac.at/research/publications/2014/Guerrero-2014-GRF/", } @article{guerrero-2008-sli, title = "Real-time Indirect Illumination and Soft Shadows in Dynamic Scenes Using Spherical Lights", author = "Paul Guerrero and Stefan Jeschke and Michael Wimmer", year = "2008", abstract = "We present a method for rendering approximate soft shadows and diffuse indirect illumination in dynamic scenes. The proposed method approximates the original scene geometry with a set of tightly fitting spheres. In previous work, such spheres have been used to dynamically evaluate the visibility function to render soft shadows. In this paper, each sphere also acts as a low-frequency secondary light source, thereby providing diffuse one-bounce indirect illumination. The method is completely dynamic and proceeds in two passes: In a first pass, the light intensity distribution on each sphere is updated based on sample points on the corresponding object surface and converted into the spherical harmonics basis. In a second pass, this radiance information and the visibility are accumulated to shade final image pixels. The sphere approximation allows us to compute visibility and diffuse reflections of an object at interactive frame rates of over 20 fps for moderately complex scenes.", month = oct, journal = "Computer Graphics Forum", number = "8", volume = "27", pages = "2154--2168", keywords = "global illumination, precomputed radiance transfer, soft shadows", URL = "https://www.cg.tuwien.ac.at/research/publications/2008/guerrero-2008-sli/", } @mastersthesis{guerrero-2008-dip, title = "Approximative Real-time Soft Shadows and Diffuse Reflections in Dynamic Scenes", author = "Paul Guerrero", year = "2007", abstract = "This thesis describes a method for approximative soft shadows and diffuse reflections in dynamic scenes, based on a method by Ren et al. [32]. An overview of precomputed radiance transfer and spherical harmonics is also presented, as well as a short introduction to global illumination. The proposed method uses a low-order spherical harmonics basis to represent incident radiance and visibility on the hemisphere of a receiver point. Diffuse reflecting geometry and shadow casting geometry is represented as sets of spheres. The spheres of an object approximate its shape and diffuse surface color as seen from any viewpoint. In a first pass, the direct illumination of an object is projected to its spheres and stored along with an approximation of the diffuse surface color as SH vectors defined over the surface of each sphere. In a second pass, the average color and the visibility for each sphere at a receiver point is found. The product of average color and visibility is used to approximate the incident radiance from diffuse reflections. Using a sphere set approximation instead of actual geometry for both soft shadows and diffuse reflections allows us to compute the visibility and diffuse reflections of an object on the fly at runtime. This text also describes a GPU implementation of the method and discusses obtained results. Interactive performance with relatively smooth framerates of over 20 fps is achieved for moderately complex scenes.", month = oct, address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", school = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", keywords = "precomputed radiance transfer, indirect illumination, global illumination", URL = "https://www.cg.tuwien.ac.at/research/publications/2007/guerrero-2008-dip/", } @studentproject{G_P_06_RFS, title = "Rendering of Forest Scenes", author = "Paul Guerrero", year = "2006", abstract = "I will discuss and compare two methods to render large forest scenes. One involves pre-generated impostors with different levels of coarseness, the other one batches up large parts of the scene according to an octree grid. Additionally, a method for LOD blending without transparency and a method for tree shading will also be presented.", keywords = "hierarchy, forest, rendering, ogre, gpu", URL = "https://www.cg.tuwien.ac.at/research/publications/2006/G_P_06_RFS/", }